IK rig breaks when I add a pole target
Okay so I'm answering my own question because I figured out the issue myself and in case anyone else has the same question they can come here for an answer if they find this.

The issue was that the rig didn't know where to bend the limb at since it was straight, which was why the leg was completely stiff. The legs need to be slightly bent so that the rig knows where exactly to bend it at.